Absorbent articles, such as infant diapers, are well known in the art. These articles are inexpensive, often disposable, and capable of absorbing and retaining fluids and other bodily discharges. Examples of prior art diapers are shown in FIGS. 1, 2, and 2a. These absorbent articles typically contain a liquid-pervious topsheet 1 manufactured from a hydrophilic material, a liquid-impervious backsheet 2 manufactured from a hydrophobic material, and an absorbent structure disposed between the topsheet 1 and backsheet 2. The absorbent structure consists of an absorbent core 3 disposed between an impervious film layer 8 and an acquisition layer 7. Prior art diapers may further include leg elastic gathers 4, leg openings 5, and elasticated barrier cuffs 6.
A serious problem associated with absorbent articles is “lateral leakage,” the leakage of body exudates out of the gaps between the absorbing article and the wearer's legs because body exudates are not immediately absorbed by the core and travel laterally across the inner surface of the diaper. One solution that has been developed to prevent lateral leakage is to elasticate the leg openings using leg elastic gathers 4 so that the absorbent article fits more securely to the wearer's thighs, thereby reducing gaps.
Another solution that has been developed is to provide elasticated barrier cuffs 6 adjacent to the absorbent core 3 and inboard of the leg elastic gathers 4 to further inhibit movement of fluids and exudates toward the leg openings 5.
There is however, a limitation to how well elasticated leg openings can fit around a wearer's thighs. This limitation is dictated by, among other things, the stiffness of the required liquid-impervious layer. Such stiff, nonwoven and plastic film laminates used to form the liquid-impervious backsheet causes resistance to the elastic strands, which limits the degree of gather formation at the leg openings, typically resulting in large gathers that leave gaps for potential leakage. Furthermore, a stiff nonwoven and plastic film laminate results in the leg opening regions becoming stiff, in turn leading to problems with fit generally and sealing in particular, as stiff, bunched material does not conform to a wearer's thighs, thus leaving gaps and increasing lateral leakage. In addition, stiffer laminates require a stronger elastic force to provide the required leg elastication, which in turn results in a stiffer seal around the wearer's thighs leading to unwanted irritation.
In addition, the use of liquid-impervious material in an absorbent article, especially in the leg opening regions of a diaper, results in decreased breathability, which in turn leads to rashes and further irritation. This is because liquid-impervious material does not permit moisture to escape, thus trapping the moisture against the wearer's thighs, resulting in rashes and irritation. It is known to form the backsheet from breathable materials, that is, materials which permit vapors to escape from the absorbent core 3 while preventing liquids and exudates from passing through. However, even when using so-called “vapor permeable” liquid barrier layers, the free escape of moist air from inside the diaper is significantly impeded by the presence of the barrier layer.
Manufacturers have made numerous attempts to construct absorbent articles capable of preventing or reducing lateral leakage. For example, U.S. Pat. No. 5,947,946 to Fisher et al. discloses a diaper consisting of a liquid-pervious topsheet 24, a liquid-impervious backsheet 26, an absorbent core 28 and elasticized leg gathers 32 to prevent lateral discharge of exudates. The length and width dimensions of the liquid-pervious topsheet and liquid-impervious backsheet are larger than the absorbent core and extend to form the outer perimeter of the diaper. The elasticized leg gathers are located laterally outboard of the absorbent core and are in between the liquid-pervious topsheet and liquid-impervious backsheet. A disadvantage with this design is the plastic backsheet which extends into the leg opening regions and results in deceased breathability in those regions and impaired fit around the leg due to the stiffness imparted by the additional layer of plastic backsheet.
Manufacturers have also made attempts to increase comfort by increasing the breathability of disposable diapers. Such attempts included the design of diapers using “zone laminates,” the use of liquid-impervious material for only a portion of the diaper's width, thus enabling diapers to be more comfortable while still being liquid-impervious in the crotch region to prevent the escape of body exudates.
For example, U.S. Pat. No. 5,263,948 to Karami et al. discloses a diaper consisting of a liquid-pervious topsheet 40, a liquid-pervious backsheet 12, an absorbent core 38, a liquid-impervious dam 28 and elasticized leg gathers 42 to prevent lateral discharge of exudates. The length and width dimensions of the liquid-pervious topsheet and backsheet are larger than the length and width dimensions of the absorbent core and liquid-impervious dam. Elasticized leg gathers are further provided between the liquid-pervious topsheet and backsheet, and located laterally outboard of the absorbent core and dam. Thus, an area surrounding the wearer's thighs consisting only of liquid-pervious material is created. A disadvantage with this design is that the liquid-impervious dam extends to, and wraps around, the side edges of the absorbent core in order to prevent body exudates from escaping through the back of the diaper or leaking through the side edges of the core. Wrapping the impervious dam around the absorbent core results in body exudates landing on the portion of the impervious material which overlays the absorbent core, causing body exudates to flow to the diaper's backsheet. A further disadvantage with this design is that the liquid-pervious topsheet is manufactured from a hydrophilic material, while the liquid-pervious backsheet is manufactured from a hydrophobic material. Thus, the region surrounding the wearer's leg consists of a combination of hydrophilic and hydrophobic material, which results in potential wetness around the wearer's legs due to the hydrophilic material wicking moisture out to its lateral edges.
An immense amount of research has been devoted to the design of absorbent articles—for example, an electronic database search for patents directed to diaper backsheet cuffs or flaps designs, run on the United States Patent and Trademark Office website, yields many hundreds of results. Despite this research, there still remains a need for a more comfortably fitting absorbent article capable of containing urinary and fecal excretions while minimizing irritation to the wearer. The present invention addresses the problems of lateral leakage and wearer irritation discussed above by providing an absorbent article with zones of: (i) reduced stiffness and (ii) continuous breathability, in the area surrounding the wearer's legs. These breathable zones of reduced stiffness improve leg gather formation and reduce irritation to the wearer's skin, resulting in a better fitting absorbent article, with reduced lateral leakage. These zones also permit the absorbent article to provide additional breathability around the leg openings, which helps prevent unwanted rashes and additional irritation.